Technical Field
This invention relates to torque shaft assemblies for moving an array of adjustable members to rotate variable stator vanes in a gas turbine engine. More particularly, it relates to torque shaft assemblies with turnbuckles or rods connecting the torque shaft to unison rings used to rotate the variable stator vanes.
Background Information
Some gas turbine engines with variable stator vanes (VSV) include a torque shaft assembly associated with an actuator. Such an assembly enables and coordinates movement of a plurality of stages of stator vanes responsive to controlled, changing engine conditions by way of crank arms connected to a unison ring for varying the angle of the vanes in each stage. A torque shaft is used to actuate the variable stator vane system of the high-pressure compressors on engines such as the General Electric LM2500+ engine. Generally, a torque shaft actuation system is advantageous in providing flexibility in stage to stage (non-linear) VSV scheduling. Examples of gas turbine engines including axial flow compressors having variable stator mechanisms are disclosed in U.S. Pat. Nos. 2,858,062, 2,933,235, and 5,281,087. Examples of torque shaft assemblies for VSVs are disclosed in U.S. Pat. Nos. 4,890,977, 6,457,937, and 6,551,057.
Torque shafts are used to actuate unison rings through adjustable length push rods or turnbuckles. Rod ends of the rods are pivotably connected to clevises mounted on torque shaft. Rolling motion caused by engine vibration may lead to premature wear of the rod ends and clevises.